1. Future directions in tropospheric chemistry – what else besides climate change Daniel J. Jacob Group photo (2013)

2. Range of tropospheric chemistry problems LOCAL < 100 km REGIONAL 100-1000 km GLOBAL > 1000 km Urban smog Plume dispersion Disasters Visibility Regional smog Acid rain Ozone layer Climate Biogeochemical cycles CLIMATE!

3. Range of tropospheric chemistry problems LOCAL < 100 km REGIONAL 100-1000 km GLOBAL > 1000 km Urban smog Plume dispersion Disasters Visibility Regional smog Acid rain Ozone layer Biogeochemical cycles

4. Jennifer’s foray into ozone smog Nitrogen oxides in the troposphere: global and regional budgets (Logan, 1983) – 508 citations The sensitivity of ozone to nitrogen oxides and hydrocarbons in regional ozone episodes (Sillman, Logan, Wofsy, 1990) -283 citations Ozone in rural areas of the United States (Logan, 1989) - 159 citations Factors regulating ozone over the United States and its export to the global atmosphere (Jacob, Logan, et al. 1993) – 150 citations This report paved the way for NO x controls! (1991)

5. Trend in 95 th percentile daytime ozone, 1990-2010 Spring Summer Cooper et al. [2012] Decrease in eastern US driven by NO x emission controls; Increase or flat in Intermountain West

6. 4 th -highest annual maximum for daily 8-h average ozone, 2008-2010 Intermountain West: The next ozone frontier! Current standard: 75 ppb Proposed standard: 60-70 ppb

7. Surface ozone at Gothic, Colorado Most ozone originates from outside N America Peak events of stratospheric influence cannot be reproduced by model Zhang et al., in prep. Numerical decay of a free tropospheric plume In GEOS-Chem Eulerian models have difficulty preserving gradients (layers) in divergent free tropospheric flow, in a way that cannot be readily fixed by increasing grid resolution or the accuracy of numerical scheme Rastigeyev et al. [2010]

8. Ammonia emission and air pollution Observed NH 4 + wet deposition fluxes can constrain NH 3 emission estimates NADP data (circles) and GEOS-Chem model after adjoint inversion April: fertilizer July: livestock kgN ha -1 month -1 Contribution of food export to annual PM 2.5 (ammonium nitrate) GEOS-Chem sensitivity simulation Fabien Paulot (in prep.)

9. Critical load exceedances for N deposition at US national parks Ellis et al. [2013] More deposition is expected to originate from ammonia in future Critical loads are 3-5 kg N ha -1 a -1 depending on ecosystem 2006 2050 NO x NH 3 Present and future (RCP) US emissions Future exceedances driven by ammonia emissions Ellis et al. [2013] 2006 2050 RCP2.6

10. Next frontier for air pollution: Nigeria OMI formaldehyde 2005-2009 MISR SCIA aerosol (AOD) NO 2 HCHO glyoxal methane Population: 270 million (+2.6% a -1 ) GDP: $273 billion (+7% a -1 ) – oil! Most natural gas is flared >80% of domestic energy from biofuel, waste Lagos Port Harcourt An unusual mix of very high VOCs, low NO x – What will happen as infrastructure develops? Eloise Marais [Harvard] gas flaring!

11. Biogeochemical cycle of mercury Hg(0) Hg(II) particulate Hg burial SEDIMENTS uplift volcanoes erosion oxidation Hg(0)Hg(II) reduction biological uptake ANTHROPOGENIC PERTURBATION: fuel combustion mining ATMOSPHERE OCEAN/SOIL VOLATILE WATER-SOLUBLE (months)lifetime ~6 months

12. History of global anthropogenic Hg emissions Large past (legacy) contribution from N. American and European emissions; Asian dominance is a recent phenomenon Streets et al., 2011

13. Global source contributions to Hg in present-day surface ocean Human activity has increased 7x the Hg content of the surface ocean Half of this human influence is from pre-1950 emissions N America, Europe and Asia share similar responsibilities for anthropogenic Hg in present-day surface ocean Amos et al., in press Europe Asia N America S America former USSR ROW pre-1850 natural emissions from biogeochemical box model constrained with GEOS-Chem fluxes

14. Disposal of Hg in commercial products: a missing component of the Hg biogeochemical cycle? Global production of commercial Hg peaked in 1970 Hannah Horowitz (Harvard)

15. Global tropospheric Br y budget in GEOS-Chem (Gg Br a -1 ) SURFACE CHBr 3 407 CH 2 Br 2 57 CH 3 Br Marine biosphere Sea-salt debromination (50% of 1-10 µm particles) STRATOSPHERE TROPOSPHERE 7-9 ppt Liang et al. [2010] stratospheric Bry model (upper boundary conditions) 56 36 Volcanoes (5-15) Deposition lifetime 7 days 1420 Sea salt is the dominant global source but is released in marine boundary layer where lifetime against deposition is short; CHBr 3 is major source in the free troposphere Parrella et al. [2012] Br y 3.2 ppt BrO 0.32 ppt

16. Bromine chemistry improves simulation of 19 th century surface ozone Standard models without bromine are too high, peak in winter-spring; bromine chemistry corrects these biases Implies that anthropogenic perturbation to global tropospheric ozone is larger than currently assumed Parrella et al. [2012]

17. Elusive understanding of what controls tropospheric OH GEOS-Chem with climatological lightning GEOS-Chem with interannual lightning (LIS) Lightning seems to be a major driver of OH variability (Murray, Logan, Jacob, 2013) LIS+OTD (satellite) lightning, 1995-2005 Tropical lightning interannual variability

18. TEMPO geostationary UV/Vis satellite instrument selected in November 2012 for 2018 launch PI: Kelly Chance, Harvard-Smithsonian Monitoring of tropospheric ozone (2 levels), aerosols, NO 2, SO 2, formaldehyde, glyoxal with 1-hour temporal resolution, 2-km spatial resoution To be part of a geostationary constellation with other sensors observing Europe and East Asia TEMPO Sentinel-4 GEMS Next frontier in satellite observations of atmospheric composition!